Arc preventing means for a switching relay



June 17, 1969 w AUER ET AL 3,451,019

ARC PREVENTING MEANS FOR A SWITCHING-RELAY Filed Jan. 8, 1968 um n h MINE f mQLHJIIIwHII E17: EL 4 ll 52-! WM "W LIH-Il I 55 I Inventors 22 William F. Auer' James J. Borzov H.

Robert L'Valleau. .B Zdaikwa (by 1 flflernegs United States Patent U.S. Cl. 335-201 3 Claims ABSTRACT OF THE DISCLOSURE Arcing between adjacent contacts of a switching relay is avoided by an insert which presents a: flange of insulating material between the contacts. The insert is a separate member, and the base of the relay is configured to easily accept the insert as one of the last assembly pieces.

This invention relates to a switching relay and in particular to a relay so constructed as to avoid arcing between contacts.

The miniaturization of switching relays has represented a significant contribution to space technology, and other technology where miniature components are of the essence in achieving usable systems involving circuit switching. The primary object of the present invention is to impart further reliability to such relays and in particular to obviate the phenomenon known as transient discharge.

In a miniature relay, operative parts are of necessity closely nested in a package no bigger than ones thumb. The stationary contacts may be separated by only a few tenths of an inch. Reliability is of paramount importance and has been achieved in most instances. However, there are some circuits where so-called transient discharge occurs in the relay with really no predictability, characterized by arcing between adjacent contacts resulting literally in an explosion. The relay is rendered utterly useless. Quality seems to be in no way involved, and every indication is that the phenomenon is completely Vagabond.

Cost of assembly of miniature relays plays a crucial role since by reduced costs, without sacrifice in quality, advances are 3111 the more promoted, and in like manner, the fewer the parts, the less probability of failure. With these factors in mind, another object of the present invention is to prevent arcing between contacts of a switching relay by a one-piece insert which may be easily disposed in place after the relay has been cleaned and as the final stage of assembly, save possibly a cover which encapsulates the relay. Specifically, in this regard, it is an object of the present invention to prevent arcing between adjacent (unrelated) stattionary contacts of a miniaturized relay by means of a separable one-piece insert interlocked with the base of the relay in a simple fashion and effective to interpose guarding flanges of insulating material between the several rows of stationary contacts, the flanges numbering one less than the number of rows of contacts. In achieving the interlock, the base is grooved, the insert flanges are nested therein, and by one means or another (preferably a spring element on the bobbin of the coil as will be explained) the insert is held in place by a positive force so that it will not be jarred loose.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and What is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawings:

FIG. 1 is a side elevation of a known form of relay to which the present invention may be addressed;

FIG. 2 is an end view taken on the line 2-2 of FIG. 1;

FIG. 3 is a perspective view of the relay shown in FIG. 1, partly assembled, but incorporating the preferred embodiment of the present invention; and

FIG. 4 is a sectional view of the relay shown in FIG. 3 but with the separated parts assembled.

The relay 10 illustrated in FIG. 1 is of known construction and in fact represents the genesis of the present invention. It will be appreciated, however, that the present invention may be applied equally well to any switching relay such as the relay 10 in FIG. 1 which includes at switch blade 12 supported on a pivotal armature 14.

The armature 14 is disposed opposite the core 16 of 'a coil 17, the coil being Wound on a plastic bobbin 18. The coil is stationary, the bobbin portion thereof being stacked to the vertical leg of an L-shaped frame 20, the upper or horizontal leg 21 of this frame extending over the bobbin and beyond the right hand end thereof. The lower end of the frame 20 is anchored to the rear end of a plastic, insulating base 22 of the relay and in which terminals and contacts are embedded as hereinafter described.

The free, outer end of the upper leg 21 of the frame 20 serves as a pivot for the armature 14 and to this end the upper margin of the armature is suitably slotted or notched as at 14N, FIG. 3, to embrace corresponding complementary projections at the free outer end of the upper leg 21 of the frame 20.

A plate 25 is riveted to the upper face of the upper frame leg 21. An ear 26 is bent upwardly at the lefthand or rear end of the plate 25. The armature 14 includes an opening 14A, FIG. 3, through which the righthand or fore end of the plate 25 extends as shown in FIG. 1 with a lug 27 bent downwardly therefrom to serve in part as a retainer for the armature, preventing displacement thereof.

The armature has a strap 30 extending across the opening 14A, and one end of a coil spring 31 is anchored thereto, the opposite end of the spring 31 being anchored to the ear 26 of the plate 25. Consequently, the spring 31 is effective to bias the armature 14 counterclockwise as viewed in FIG. 1 so that a contact element 35 at the lower end of the switch blade 12 engages a corresponding stationary contact extending upwardly from the base 22 of the relay.

The switching blade 12 is compound in nature as shown in FIG. 2 in that there are a plurality of switch fingers 12A, 12B, 12C and 12D each presenting a contact as 35 adapted to conduct current independently of the other switch fingers as represented by the individual conductor wires 36A, 36B, 36C and 36D to the upper ends thereof. The wires 36A-36D are connected to terminals or posts as 38 embedded in the plastic base 22, and the coil 17 receives current through wires as 39 which in turn are connected to terminals 40 in the plastic base. When the coil is energized, the armature 14 is attracted to the core 16, pivoting clockwise against the bias of spring 31, whereby the contacts of the switch blade disengage some of the stationary contacts on the base and engage others.

Just as there are a plurality of switch fingers included in the switch blade 12, so there are as many pairs of stationary contacts supported in the insulating base 22 of the relay. Thus, as best shown in 'FIG. 3, the contacts as to which switching is to occur through movement of the switch blade 12 are arranged in the base 22 in pairs position C and a pair at position 40]). Ordinarily, with the coil unenergized, the switch blade 12 is positioned as shown in FIG. 1 where the contacts 35 thereof are engaged in electrical series with the right-hand ones of the stationary contacts; but when the coil is energized the armature responds, moving clockwise as viewed in FIG. 1. The right-hand contacts are disengaged and the contacts 45,. FIG. 1, carried by the switch blade 12, are moved into engagement with the left-hand ones of the stationary contacts presented on the insulating base.

It maybe assumed that the circuits represented by the adjacent rows of stationary contacts are unrelated in the sense of being independent of one another, but in a relay of the size here involved, itself smaller than ones thumb, the stationary contacts in adjacent rows are quite close one to another, but not so close that arcing between the unrelated contacts would ordinarily occur. However, undesired arcing can and does occur in some circuits without any predictability. Under certain test parameters, a relay such as shown in FIG. 1 may operate over an indefinite number of cycles without any transient discharge or arcing between the unrelated contacts; but in a separate test, transient discharge accompanied by utter failure of the relay may occur after 1500 cycles or even less. The phenomenon appears to be completely vagabond in nature, and is not due to poor quality. In fact, it is desirable to preserve the known construction as much as possible, and in accordance with the present invention We take positive steps to prevent arcing by interposing a barrier of such form, construction and relation to the relay as a whole as to enable all other features of the relay to be preserved, and without the necessity of resorting to additional parts, with the sole exception of a separable insert which itself presents the barrier.

Thus, referring to FIG. 3, this is a perspective view of the same relay shown in FIG. 1, but modified to the extent of additional slots in the base 22 and the afiixation of a spring element to the bobbin of the coil. Insofar as these features are concerned, no additional tooling or real expense is involved, which is to say that neither the bobbin nor the base is altered in any material sense since these themselves are molded parts. Thus, and referring to FIG. 3, the upper face of the base 22 is formed with three elongated slots -1, 50-2 and 50-3, the slots being formed between and parallel to the adjacent rows of stationary contacts so that there is one less slot (three) than the number of rows of stationary contacts which happens to be four in this instance. t

The barrier for preventing arcing is in the form of a separable molded plastic insulating member 52, FIG. 3, which presents three insulating barrier flanges 52-1, 52-2 and 52-3 parallel to one another and spaced apart a distance corresponding to the spacing between the slots in the base, the flanges just described being integrally joined to a transverse web or strap 54. The flanges, as the slots, number one less than the number of rows of stationary contacts.

. It will be observed in FIG. 3 that the middle slot 50-2 is a through slot in that it opens at the forward edge of the plastic base 22, serving as a guide as will be explained. The other two slots are dead-end slots, and in this connection the flanges 52-1 and 52-3 are formed with notches as 55, FIGS. 3 and 4, adjacent the web 54 and which embrace the shoulders 56 on the base 22 which result from the slots 50-1 and 50-3 being of dead-end form. Thus, the barrier insert 52 is adapated to be so aligned with the front of the base 22 that the middle flange 52-2 fits into the open end of the middle slot 50-2. This facilitates assembly. The insert as a whole is then guided home, and can be pressed into place once the notches as 55 clear the shoulders as 56 to establish one form of interlock. The lower edges of the barrier flanges are then 4 neatly confined in the corresponding slots in the base a shown in FIG. 4, thereby establishing an interlock between the barrier and the base, each separate flange of the insert 52 being disposed, as it is, between adjacent contacts, thereby being effective to prevent arcing or transient discharge across. the unrelated contacts. Of course the flanges are of such height and length as to effectively shroud one row of contacts from another so that no arc can jump the gap, which indeed is closed.

A relayof the kind involved includes a dust-proof cover 60, FIG. 4, which is the'last part assembled. It will be noted that we bring the web 54 of the insert flush with the front edge of the base 22, and the inside face of the cover 60 engages the insert. There can, therefore, be no displacement of the insert 52 following complete assembly with the cover in place, and in this connection it should be noted that the insert itself is set in place only after the working parts of the relay have been assembled and cleaned as an incident to final inspection. If desired,

one or more lugs 60L, FIG. 4, maybe molded on the inside of the cover to bear on the top of the web 54 of the barrier insert 52, and it will be appreciated that the cover has a tight fit on the base 22.

We prefer, nevertheless, to establish a firm, positive interlock so that the insert 52 will not be jarred loose when the cover is assembled, and to this end the bobbin 18, at the forward end thereof, may be provided with a separately attached or integrally molded tab 18T so dimensioned and configured as to bear with spring force on the barrier insert 52. Thus, as shown in FIG. 3, in which certain parts of the relay are removed for clarity, the spring tab 1ST, prior to installation of the barrier insert, is bent well forward and is positioned to engage one of the flanges of the insert, preferably the middle flange 52-2 notched at 62 to enable the spring tab 18T to neatly fit thereagainst. As shown in FIG. 4, when the insert 52 is in its proper home position, the spring tab 18T is flexed rearwardly, bearing forcefully with spring action against the shoulder of the middle flange 52-2 defined by the notch 62 therein, whereby the insert is biased forcefully with spring action causing the insert to bear forcefully against the shoulders 56 presented at the fore ends of the outside slots 50-1 and 50-3. Other modes of spring action can be used of course, but superior results with little alteration in the known construction are attained in the manner just described. In fact, it is conceivable that with an appropriate thin and flexible construction the insert could be held in place by distortion itself characterizing a full snap-action fit, but a possible disadvantage to this is that the person completing the assembly may use too much force or experience a slipped finger causing damage to the relay.

It will be seen from the foregoing that we have greatly enlarged the reliability of a miniaturized relay by taking steps to obviate the wholly unpredictable phenomenon of cross-arcing between unrelated stationary contacts. We accomplish this by means of a one-piece insert that presents insulating flanges between the rows of stationary contacts of sufllcient length and height as to effectively block the existing gaps. Reliability is a critical factor, especlally in systems involving space vehicles, and we assure this while facilitating assembly and preventing dislodgement of the insert by using a spring action to hold the insert in place, preferably by a small spring tab on the bobbin of the coil bearing against an extension of one of the insert flanges. The relay we have chosen for illustra tion is but one of many in which the present invention may be embodied; and hence while we have illustrated and described a preferred embodiment of the present invention it is to be understood that this is capable of variation and modification within the purview of the appended claims.

We claim:

1. In a switching relay having a fixed coil and an armature-mounted switch blade responsive to energization of the coil for switching circuits represented by a plurality of paired stationary upstanding contacts supported on the base of the relay in adjacent rows between which stationary contacts undesired arcing can occur: means for preventing arcing between contacts in adjacent rows and comprising a separable one-piece insert presenting a plurality of flanges of insulating material respectively disposed between and shrouding the contacts in adjacent rows one from another, the base of the relay being slotted with a lower portion of the insert slidably nested therein, and means including spring means acting between the relay and the insert to hold the insert in place.

2. A relay according to claim 1 in which the insert is formed with at least one notch embracing a corresponding shoulder on the relay base and in which the spring means is mounted on the coil and bears on the end of the insert opposite the notch to press a wall of the notch against the shoulder thereby holding the insert in place following assembly of the insert.

3. A relay according to claim 2 in which a lower edge of each flange fits in a slot in the relay base, in which one of the flanges is longer than the others, and in which the slot for the longer flange is open-ended to enable the insert to be guided into assembled position.

References Cited UNITED STATES PATENTS 1,795,641 3/1931 Dante. 3,179,771 4/1965 McGary. 3,295,078 12/ 1966 Hrynewycz.

GEORGE HARRIS, Primary Examiner.

US. Cl. X.R. 

